Experiments on effects of thread rolling accuracy on rock bolt pretension
Abstract：Based on analysing the relation between the nut torsion moment and rock bolt pretension,the influence of the thread rolling accuracy upon the pretension was investigated.Factors influencing the thread rolling efficiency,i.e.,rock bolt material quality,rolling technology and equipments,were examined.To study the relationship between torque and pretension,a laboratory table was specially designed and a series of tests were carried out on the rock bolts with different thread accuracy.The result indicates that the higher the thread rolling accuracy,the higher the coefficient of torque-to-pretension conversion.And the coefficient can be improved by daubing lubrication oil on the thread.In China,the rock bolt thread encounters the issue of low rolling accuracy which results in coarse thread surface.As a result,the efficiency of the torque-to-pretension conversion is greatly reduced.In addition,the rock bolt is susceptible to break at the thread end.Essential approach to resolve these issues is to significantly improve the thread rolling accuracy by adopting advanced equipment.
Keywords：rock boltsthread rolling accuracypretensiontorsion momentconversion coefficient
Publication Date：2011-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)